Help! Zebra danios terrorising newly-added neon tetras

[Yossu]

We have a tropical aquarium (24"x12"x12", internal Eheim filter) which until today had an angel, two zebra danios and a guppy. They were moved into this tank about a week ago and all seemed peaceful and settled.

Today, we introduced 12 small neon tetras. We kept the lights and air pump off, but as soon as they were added, the angel and danios started chasing them around. The angel seems to have got bored with that fairly quickly, but seven hours later, the danios are still chasing them around. I haven't actually seen them attack a neon, but they chase them around, and charge into the middle of the shoal a lot.

Is this normal? I thought danios were fairly peaceful fish. They always were before!

Thanks for any advice you can give.

 

[jaylach]

If the zebra danios are mature they are probably large enough to the neons as a food source.

 

[Yossu]

@jaylach We've had them for a couple of years, but they aren't big enough to get a neon in their mouths. I thought of that before buying them.

Thanks

 

[jaylach]

OK, I don't really know the fish but did a search and saw that they can reach 2.5 inches and even up to 3 inches but going back and reading further the average is only around 1 inch.

 

[Yossu]

@jaylach I would say an inch is about right for ours. That's why I wasn't worried about putting the neons in, as I didn't think the danios would be able to eat them.

As I said, I haven't seen them actually attack, they just chase the neons around.

Any ideas? Thanks again.

 

[jaylach]

Not having experience with the fish there is not much advice for me to give. I'm sure that others that know the fish will chime in.

Likely it is a territorial thing and boundaries are being established.

 

[Essjay]

With just 2 of them, you won't see normal behaviour from the danios. They are shoaling fish which need to be in a bigger group and the stress from not being in a big enough group affects their behaviour. Some species will become very timid and hide all the time while other species will become more aggressive.

However, in a tank this size getting more danios is not a good idea as the tank is now fully stocked. The angel will need a much bigger tank before long.

 

[GaryE]

Zebras have small mouths. Eating is not an issue.
Chasing is what they do with each other, in shoals of 10 or so fish. They are trying to get the neons to act like normal fish (to them). The neons are not going to. It isn't aggression, it's a kind of twisted welcome. They are too few to be happy with life, and they are trying to get a calmer, slower fish to run with them.
if there were more danios, they would probably ignore the neons.

 

[Yossu]

Thanks to all of you for the replies. As it happens, it seems a lot calmer now. Whether that's going to last or not remains to be seen!

Didn't realise danios were shoaling. Bit late now unfortunately.

 

[Colin_T]

you could return the danios

 

[Yossu]

you could return the danios

Nah, had them for a couple of years. Not even sure where I bought them now.

Anyway, I'm glad to say that things are a lot more settled today. The danios still dart around the tank, but then they always did, but they don't seem to be bothering the neons nows.

Thanks to all for the help